NUMERICAL MODELING FOR MINIMUM DEPTH DETERMINATION ON THE USE OF KIRSCH EQUATION FOR CALCULATION OF STRESS DISTRIBUTION AROUND TUNNEL

• Main Author: Mega Trisnawati, Afrilia
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/56510
• Institution: Institut Teknologi Bandung

The purpose of tunnels can be varied. It makes determining the tunnel’s location and dimension that will be excavated vary too. Therefore, before initiating an excavation on rock masses, performing an analysis of stress that works on the rock masses is required. This hampered stress needs to be put in consideration. Kirsch equation (1898) can be used to calculate the value of the rock masses’ stress around the tunnel. However, Kirsch equation (1898) can not be used in every tunnel’s condition, this equation has the requirement of only to be used on several condition, one of which is the depth of the tunnel. In this research, a stress distribution analysis is carried out around the tunnel to determine the minimum depth in order to make Kirsch equation (1898) relevant to be used. The matter that is to be observed is the tangential stress on the roof and the wall of the tunnel at the excavation boundary at various depth and K value. The result from using numerical method calculation will be compared with the result from Kirsch equation (1898) calculation, afterwards it will be analysed to determine the minimum depth of using Kirsch equation. The result from both method shows the differences, the biggest one located on the tunnel depth of lesser than 20R and become constant after the tunnel enter the depth of 20R, so the minimum depth by using Kirsch equation is 20R calculated from the centre of the tunnel to the surface. The difference in result of numerical method to the Kirsch equation can be seen on the roof of the tunnel both for K=1 and K=2 and on the wall, the difference is small. The tunnel’s roof for K=1 has the difference of 33% while for K=2 has the difference of 20%. The difference in result is due to several factors like Kirsch equation (1898) in which the equation generalize stress on the rock masses as hydrostatic and numerical method in which the circle cross section can not form perfect circle.